1. Field of the Invention
The present invention relates to a temperature control method of a refrigerator, and more particularly to a temperature control method of the refrigerator for controlling a temperature in a refrigerating chamber.
2. Description of the Prior Art
A refrigerator is usually composed of a refrigerating chamber and a freezing chamber.
The refrigerator thus divided into the refrigerating chamber and the freezing chamber operates such that cold air of the freezing chamber is supplied to the refrigerating chamber.
The cold air is controlled by a damper disposed at a passage for connecting the refrigerating chamber to the freezing chamber through which cold air is supplied from the freezing chamber to the refrigerating chamber.
FIG. 1 is a block diagram of a temperature control circuit in a conventional refrigerator thus described.
In FIG. 1, reference numeral 10 is an operating unit comprising a temperature control switch (or lever) for setting temperatures in the refrigerating chamber, freezing chamber and the like of the refrigerator by way of instructions inputted by a user.
Reference numeral 20 is a temperature sensing unit for sensing the temperatures by way of temperature sensors disposed at the refrigerating chamber, freezing chamber and the like.
Reference numeral 30 is a damper sensing unit for sensing an opening and closing of the damper for supplying or cutting off the cold air to the refrigerating chamber and the like.
Reference numeral 40 is a control unit for outputting a predetermined control signal for controlling the refrigerator according to outputs of the operating unit 10, temperature sensing unit 20 and the damper sensing unit 30.
Reference numeral 50 is a display unit for operating in accordance with the control signal output from the control unit 40 and to display the state of the refrigerator.
In other words, the display unit displays the temperatures of the refrigerating chamber, freezing chamber and the like.
Reference numeral 60 is a damper driving unit for operating the damper according to the control signal output from the control unit 40.
In the refrigerator having the temperature control circuit mentioned above, the user sets the temperatures in the refrigerating chamber, freezing chamber and the like by way of an operation unit 10. The temperature set by the user can be termed a target temperature. The selecting of a target temperature automatically results in the creation of a target temperature range having upper and lower limits or reference temperatures Tr1 and Tr2.
When the temperature is set by the user, the control unit 40 compares reference temperature with the detected temperature in the refrigerating chamber or freezing chamber by way of the temperature sensing unit 20.
As a result of that comparison, if the detected temperature detected by the temperature sensing unit 20 reaches the first reference temperature Tr1 as illustrated by a solid line in FIG. 2, the control unit 40 outputs the control signal to the damper driving unit 60 to thereby open the damper, so that the cold air in the freezing chamber can be supplied to the refrigerating chamber.
If the detected temperature reaches the second reference temperature Tr2 as the temperature in the refrigerating chamber goes down due to opening of the damper, the control unit 40 outputs the control signal to the damper driving unit 60 to thereby close the damper, so that the cold air of the freezing chamber supplied to the refrigerating chamber can be cut off.
If supply of the cold air to the refirgerating chamber is cut off due to the close-down of the damper, the temperature of the refrigerating chamber in turn rises up with time.
If the detected temperature in the refrigerating chamber rises up again to thereby reach the first reference temperature Tr1, the damper is opened as described in the foregoing and the cold air is supplied to the refrigerating chamber to thereby lower the temperature of the refrigerating chamber.
As seen from the foregoing, the temperature in the refrigerating chamber varies around the target value To according to the control of the damper by way of the first and second reference temperatures Tr1 and Tr2.
However if an outside temperature of the refrigerator rises up above a predetermined value, there arises a difference between the temperature in the refrigerating chamber detected by the temperature sensing unit 20 and an actual temperature in the refrigerating chamber, due for instance to a time delay between the rising of the actual temperature and the detecting thereof.
In other words, as illustrated in FIG. 2 by the solid lines, the actural temperature in the refrigerating chamber is detected to have reached the first reference temperature Tr1, so that the control unit 40 outputs the control signal to the damper driving unit 60 to thereby open the damper, notwithstanding that the actual temperature in the refrigerating chamber actually was a higher first temperature Te1.
Furthermore, the temperature in the refrigerating chamber is detected to have reached the second reference temperature Tr2, even though the actual temperature was at a higher second temperature Te2, so that the control unit 40 outputs the control signal to the damper driving unit 60 to thereby close the damper at a time which is subsequent to an optimum time for doing so.
As described above, when the outside temperature is above a predetermined value, the temperature in the refrigerating chamber cannot be accurately detected as the outside temperature rises up, whereby the actual temperature in the refrigerating chamber varies around a target temperature value Teo which is higher than the desired target value To.
Accordingly, because the actual temperature of the refrigerating chamber has the predetermined temperature difference (Teo-To), there arises a problem in that the freshness of food stored in the refrigerating chamber deteriorates.
Furthermore, because the user establishes the temperature in the freezing chamber or refrigerating chamber by way of the operation unit 10 (Usually, established ranges are "strong", "intermediate strong", "intermediate", "intermediate weak" and "weak".), there also arises a problem in that the established temperature cannot be accurately detected by the user at the control unit 40 due to electrical noise and the like.
At this time, there usually arises a problem in that erroneous operations are conducted by the control unit 40 because the established temperatures are erroneously interrupted as temperatures situated out of the range which can be achieved by the refrigerator.
Still furthermore, a large amount of cold air should be supplied to the freezing chamber during a quick cooling when the food stored in the freezing chamber is required to be cooled quickly. However, there usually arises a problem in that the quick cooling is not properly realized in the freezing chamber because the damper is caused to open to thereby supply the cold air to the refrigerating chamber when the temperature in the refrigerating chamber reaches the second reference temperature (Tr2) even in the. quick freezing mode.
Meanwhile, a baffle is disposed on the damper for controlling the cool air supplied to the refrigerating chamber, whereas the baffle is closed or opened by rotation of a cam to thereby supply or cut off the cold air to the refrigerating chamber.
At this time, the opening and closing states of the baffle are detected by: a magnet disposed at one end of the cam; a lead switch for being opened or closed when the magnet is approached or distanced thereform according to the closing and opening of the baffle; and a control unit for determining whether the baffle is in a closed or opened state by way of detection of the lead switch being closed or opened.
As mentioned above, the damper, in its operational characteristic when the cam is rotated to thereby open the baffle, causes the lead switch to closed, thereby causing the control unit 40 to determine that the baffle is open.
However, when the cam is rotated to open the closed baffle, the magnet becomes distanced from the lead switch, whereby a contact of the lead switch may become short-circuited before the baffle is fully opened to thereby cause the control unit 40 to determine that the baffle is completely opened.
Furthermore, when the baffle is required to be closed, the magnet approaches the lead switch and may open the contact of the lead switch before the baffle is completely closed, thereby causing the control unit 40 to determine that the baffle is entirely closed.
As described above, because the control unit 40 cannot accurately discriminate whether the baffle of the damper is in operation, there arises a problem in that control of the damper is not accurately performed.